This invention relates to an electromagnetic read/write structure for the reading and writing of magnetic images on a relatively moving magnetic recording medium. More specifically, it relates to a unique, unitary, integrated read/write head/flexure/conductor structure of extremely small size, and to a method of making the same. In characterizing the size of the proposed structure, I think of the same as a micro flexhead.
While the structure of the invention may be used in a wide variety of applications, a preferred embodiment of the same is described herein in conjunction with reading and writing images with respect to rigid recording media, such as a disk or drum, in which application it has been found to have particular utility and to offer special advantages.
The performance of magnetic recording systems improves rapidly as the separation between the read/write head and the associated recording medium decreases. In rigid media systems, today, this separation is referred to as "flying height"--a reference relating to the fact that the conventional head, often referred to as a slider, is supported above the relatively moving medium surface by an air bearing. As the flying height is reduced, the risk of head wear, and in particular the potential for catastrophic wear or head "crash", increases rapidly. This problem may, of course, be minimized by proper selection of slider and medium surface materials relating to hardness, coefficient of friction, thermal conductivity, etc., and also by paying proper attention to the quality of the head/media interface, lubrication and the elimination of contaminants which may appear in that interface.
Nonetheless, in a typical system of this type currently, the head structure contacts the moving medium in the start and stop process, and occasionally in the operating mode, resulting, inevitably, in some degree of abrasive if not catastrophic wear. In general, wear rate is dependent upon surface velocity and applied pressure and, for a given velocity, increases slowly with pressure. However, at some point the wear rate rises steeply, resulting in some form of catastrophic wear.
One difficulty in understanding the wear process and in limiting wear, particularly in low flying heads on rigid media, is that the area of contact is frequently orders of magnitude smaller than that of the "footprint" of the slider. This is due to one or more of a variety of factors, such as roll and pitch dynamics, or the presence of a foreign particle in the head/medium interface. As a consequence, the transient local contact pressure, resulting from applied load plus inertial forces, may become extremely large. Looking at this situation a bit more closely, a key point is that such microscopic regions of contact are largely independent of the size and mass of the slider and, since reduction of the size and mass of the slider enables a corresponding reduction in the applied load and inertial forces, local contact pressure may be reduced accordingly.
Another reason for reducing the footprint of a slider as head/medium separation is reduced relates to the fact that slider roll or non-flatness of the medium or slider surface may cause the tip of the read/write pole to be abnormally separated from the medium.
Reducing the size, mass and applied load of a slider, of course, requires appropriate attention to the design of the air bearing of the slider, namely, a reduction of the slider's surface corresponding to the reduced applied load, in order to maintain the desired flying height. Also to be noted is the fact that the constraint on size and mass reduction of a slider with conventional designs lies in the practical limitations of fabricating slider bodies, air bearing rails and gimble-flexures mechanisms with appropriately small dimensions and tolerances, and mounting the sliders on flexures with correspondingly tight tolerances. Ultimately, the minimum size and mass is determined by the dimensions of the transducer, electrical conductors and supporting structure. Present sliders are one to two orders of magnitude larger in size than the transducer itself, and as much as three orders of magnitude larger in mass. Thus, in principle, the mass, and therefore the local contact pressure, could potentially be reduced by about three orders of magnitude, thereby greatly reducing abrasive wear, and perhaps also eliminating the possibility of a head crash.
In summary, major advances in the performance of medium magnetic recording systems may be achieved by further reducing head/medium separation--ultimately to continuous sliding contact. However, reducing head/medium separation, other things being the same, results in an increased abrasive wear, and in a greater risk of catastrophic wear. Since the area of contact between a slider and a medium is typically very small and relatively independent of the slider's macrodimensions, it should be possible to reduce greatly the size and mass of the slider, thus to enable a corresponding reduction in the applied and inertial forces and the local contact pressure, all resulting in greatly reduced abrasive wear and lower risk of catastrophic wear. Reduced footprint dimensions of a slider would also help to maintain small separation between the head and medium.
A general object of the present invention, therefore, is to provide a unique read/write structure and a unique, related manufacturing method which deal with each of the issues addressed above in a novel and extremely effective manner.
Specifically, an object of the invention is to provide a unique read/write structure (and a special method of manufacturing the same) which structure is orders of magnitude smaller in size and mass when compared with today's counterparts--a structure which is capable of non-catastrophic, continuous sliding contact interaction with the surface of a relatively moving recording medium.
Yet another object of the invention is to provide such a structure and method which are characterized by a unitary and totally integrated head/flexure/electrical conductor combination formed entirely, atom-by-atom, in a deposition process, e.g. by sputtering and photolithographic patterning of materials.
A further object is to provide a structure which easily allows for multiple-head arrays.
Still another important object of the invention is to provide a novel method of manufacturing a read/write structure of the types just generally outlined.
An object related to the immediately pre-stated object is to provide a unique method of manufacture, wherein different portions of the necessary magnetic substructure within the overall structure are formed on generally orthogonally related planes, in order to permit very precise, small-dimension, dimensional control, and wherein further, a readily etchable structure-supporting base layer, as well as readily, commonly etchable boundary walls, positioned between adjacent flexure structures during the manufacture of plural structures, are formed to promote, cooperatively, greatly simplified ultimate separation (singulation) of individual flexures.
These and other important objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.